Stride adjustment mechanism

ABSTRACT

In an elliptical step exercise apparatus a dynamic link mechanism can be used to vary the stride length of the machine. A control system can also be used to vary stride length as a function of various exercise and operating parameters such as speed and direction as well as varying stride length as a part of a preprogrammed exercise routine such as a hill or interval training program. In addition the control system can use measurements of stride length to optimize operation of the apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation in part of U.S. Non-Provisionalpatent application Ser. No. 09/835,672, filed Apr. 16, 2001 now U.S.Pat. No. 6,846,272 and Ser. No. 10/787,788, filed Feb. 26, 2004 now U.S.Pat. No. 7,435,202 and claims priority on U.S. Provisional PatentApplications Ser. No. 60/450,812, filed Feb. 27, 2003 and Ser. No.60/501,988, filed Sep. 11, 2003.

FIELD OF THE INVENTION

This invention generally relates mechanisms to control exerciseequipment and in particular to programs for controlling strideadjustment of elliptical exercise equipment.

BACKGROUND OF THE INVENTION

There are a number of different types of exercise apparatus thatexercise a user's lower body by providing a circuitous stepping motion.These elliptical stepping apparatus provide advantages over other typesof exercise apparatuses. For example, the elliptical stepping motiongenerally reduces shock on the user's knees as can occur when atreadmill is used. In addition, elliptical stepping apparatuses exercisethe user's lower body to a greater extent than, for example,cycling-type exercise apparatuses. Examples of elliptical steppingapparatuses are shown in U.S. Pat. Nos. 3,316,898; 5,242,343; 5,383,829;5,499,956; 5,529,555, 5,685,804; 5,743,834, 5,759,136; 5,762,588;5,779,599; 5,577,985, 5,792,026; 5,895,339, 5,899,833, 6,027,431,6,099,439, 6,146,313, and German Patent No. DE 2 919 494.

An important feature in an elliptical stepping apparatus is the abilityto adjust stride length. Naturally, different people have differentstride lengths and the exercise apparatus needs to accommodate each userso that they have a more comfortable and efficient workout. It is alsoimportant that the user can change the stride length during theoperation of the elliptical stepping device. When the user increases thespeed, then naturally he will have a longer stride length and themachine needs to adjust to this change in length. A problem withelliptical exercise machines used in the past is that they can notadjust horizontal stride length without significantly changing verticalheight of the foot motion. It is therefore advantageous for the user tominimize the vertical displacement of the footpath when stride lengthchanges because it allows for more natural and comfortable motion.

SUMMARY OF THE INVENTION

It is therefore an object of the invention to minimize the verticaldisplacement of the footpath when the stride length changes.

A further object of the invention is to use a dynamic link mechanism toadjust stride length which allows for a smooth transition of stridelengths during operation and minimizes the vertical displacement whenstride length changes.

A still further object of the invention is to allow a runner to adjustcadence independently while changing stride length.

An additional object of the invention is to allow the use sensors and aprocessor to compare stride lengths of the left and right pedal andautomatically adjust them to be equal.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side perspective view of an elliptical stepping exerciseapparatus;

FIG. 2 is a schematic and block diagram of representative mechanical andelectrical components of an example of an elliptical stepping exerciseapparatus in which the method of the invention can be implemented;

FIG. 3 is a plan layout of a display console for use with the ellipticalexercise apparatus shown in FIG. 2;

FIGS. 4 and 5 are views of the preferred embodiment of dynamic linkmechanism for use in adjusting stride length in an elliptical steppingapparatus of the type shown in FIG. 1;

FIGS. 6 and 7 are views of the secondary embodiment of dynamic linkmechanism for use in adjusting the stride length in an ellipticalstepping apparatus of the type shown in FIG. 1;

FIGS. 8A, 8B, 8C and 8D are schematic diagrams illustrating theoperation of the dynamic link mechanism of FIGS. 4-7 for a 180 degreephase angle;

FIGS. 9A, 9B, 9C and 9D are schematic diagrams illustrating theoperation of the dynamic link mechanism of FIGS. 4-7 for a 60 degreephase angle;

FIGS. 10A, 10B, 10C and 10D are schematic diagrams illustrating theoperation of the dynamic link mechanism of FIGS. 4-7 for a zero degreephase angle;

FIG. 11 is a pair of perspective view of a linear guide assembly for usewith the mechanisms of FIGS. 4-7;

FIG. 12 is a view of an additional embodiment for a stride adjustmentmechanism;

FIG. 13 is a side view of the elliptical exercise apparatus with adifferent stride adjustment mechanism than shown in FIG. 1;

FIG. 14-16 are views of different actuators for use in the strideadjustment mechanisms;

FIGS. 17A, 17B and 17C are a set of schematic diagrams illustratingangle measurements that can be used to determine stride length in anelliptical stepping apparatus of the type shown in FIG. 4; and

FIG. 18 is perspective view of mounting assembly for use with thedynamic linck mechanism of FIGS. 4 and 5.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a representive example of an elliptical step exerciseapparatus 10 of the type that can be modified to have the capability ofadjusting the stride or the path of the foot pedal 12. The exerciseapparatus 10 includes a frame, shown generally at 14. The frame 14includes vertical support members 16, 18A and 18B which are secured to alongitudinal support member 20. The frame 14 further includes crossmembers 22 and 24 which are also secured to and bisect the longitudinalsupport member 20. The cross members 22 and 24 are configured forplacement on a floor 26. A pair of levelers, 28A and 28B are secured tocross member 24 so that if the floor 26 is uneven, the cross member 24can be raised or lowered such that the cross member 24, and thelongitudinal support member 20 are substantially level. Additionally, apair of wheels 30 are secured to the longitudinal support member 20 ofthe frame 14 at the rear of the exercise apparatus 10 so that theexercise apparatus 10 is easily moveable.

The exercise apparatus 10 further includes the rocker 32, an attachmentassembly 34 and a resistance or motion controlling assembly 36. Themotion controlling assembly 36 includes the pulley 38 supported byvertical support members 18A and 18B around the pivot axle 40. Themotion controlling assembly 36 also includes resistive force and controlcomponents, including the alternator 42 and the speed increasingtransmission 44 that includes the pulley 38. The alternator 42 providesa resistive torque that is transmitted to the pedal 12 and to the rocker32 through the speed increasing transmission 44. The alternator 42 thusacts as a brake to apply a controllable resistive force to the movementof the pedal 12 and the movement of the rocker 32. Alternatively, aresistive force can be provided by any suitable component, for example,by an eddy current brake, a friction brake, a band brake or a hydraulicbraking system. Specifically, the speed increasing transmission 44includes the pulley 38 which is coupled by the first belt 46 to thesecond double pulley 48. The second double pulley 48 is then connectedto the alternator 42 by a second belt 47. The speed increasingtransmission 44 thereby transmits the resistive force provided by thealternator 42 to the pedal 12 and the rocker 32 via the pulley 38. Thepedal lever 50 includes a first portion 52, a second portion 54 and athird portion 56. The first portion 52 of the pedal lever 50 has aforward end 58. The pedal 12 is secured to the top surface 60 of thesecond portion 54 of the pedal lever 50 by any suitable securing means.In this apparatus 10, the pedal 12 is secured such that the pedal 12 issubstantially parallel to the second portion of the pedal lever 54. Abracket 62 is located at the rearward end 64 of the second portion 54.The third portion 56 of the pedal lever 50 has a rearward end 66.

In this particular example of an elliptical step apparatus, the crank 68is connected to and rotates about the pivot axle 40 and a roller axle 69is secured to the other end of the crank 68 to rotatably mount theroller 70 so that it can rotate about the roller axle 69. The extensionarm 72 is secured to the roller axle 69 making it an extension of thecrank 68. The extension arm 72 is fixed with respect to the crank 68 andtogether they both rotate about the pivot axle 40. The rearward end ofthe attachment assembly 34 is pivotally connected to the end of theextension arm 72. The forward end of the attachment assembly 34 ispivotally connected to the bracket 62.

The pedal 12 of the exercise apparatus 10 includes a toe portion 74 anda heel portion 76 so that the heel portion 76 is intermediate the toeportion 74 and the pivot axle 40. The pedal 12 of the exercise apparatus10 also includes a top surface 78. The pedal 12 is secured to the topsurface 60 of the pedal lever 50 in a manner so that the desired footweight distribution and flexure are achieved when the pedal 12 travelsin the substantially elliptical pathway as the rearward end 66 of thethird portion 56 of the pedal lever 50 rolls on top of the roller 70,traveling in a rotationally arcuate pathway with respect to the pivotaxle 40 and moves in an elliptical pathway around the pivot axle 40.Since the rearward end 66 of the pedal lever 50 is not maintained at apredetermined distance from the pivot axis 40 but instead follows theelliptical pathway, a more refined foot motion is achieved. It should beunderstood however that the invention can be implemented on otherconfigurations of elliptical step apparatus having a variety ofmechanisms for connecting the pedal lever 50 to the crank arm 68including a direct attachment.

FIG. 2 is a combination schematic and block diagram that provides anenvironment for describing the invention and for simplicity shows inschematic form only one of two pedal mechanisms typically used in anelliptical stepping exercise apparatus such as the apparatus 10. Inparticular, the exercise apparatus 10 described herein includes motioncontrolling components which operate in conjunction with an attachmentassembly to provide an elliptical stepping exercise experience for theuser. Included in this example of an elliptical stepping exerciseapparatus 10 are the rocker 32, the pedal 12 secured to the pedal lever50, the pulley 38 supported by the vertical support members 18A and 18Band which is rotatable on the pivot axle 40. This embodiment alsoincludes an arm handle 80 that is connected to the rocker 32 at a pivotpoint 82 on the frame of the apparatus 10. The crank 68 is generallyconnected to one end of the pedal lever 50 by an attachment assemblyrepresented by the box 34 and rotates with the pulley 38 while the otherend of the pedal lever 50 is pivotally attached to the rocker 32 at thepivot point 84.

The apparatus 10 as represented in FIG. 2 also includes resistive forceand control components, including the alternator 42 and the speedincreasing transmission 44 that includes the pulley 38. The alternator42 provides a resistive torque that is transmitted to the pedal 12 andto the rocker 32 through the speed increasing transmission 44. Thealternator 42 thus acts as a brake to apply a controllable resistiveforce to the movement of the pedal 12 and the movement of the rocker 32.Alternatively, a resistive force can be provided by any suitablecomponent, for example, by an eddy current brake, a friction brake, aband brake or a hydraulic braking system. Specifically, the speedincreasing transmission 44 includes the pulley 38 which is coupled by afirst belt 46 to a second double pulley 48. A second belt 47 connectsthe second double pulley 48 to a flywheel 86 of the alternator 42. Thespeed increasing transmission 44 thereby transmits the resistive forceprovided by the alternator 42 to the pedal 12 and the rocker 32 via thepulley 38. Since the speed increasing transmission 44 causes thealternator 42 to rotate at a greater rate than the pivot axle 40, thealternator 42 can provide a more controlled resistance force. Preferablythe speed increasing transmission 44 should increase the rate ofrotation of the alternator 42 by a factor of 20 to 60 times the rate ofrotation of the pivot axle 40 and in this embodiment the pulleys 38 and48 are sized to provide a multiplication in speed by a factor of 40.Also, size of the transmission 44 is reduced by providing a two stagetransmission using pulleys 38 and 48.

FIG. 2 additionally provides an illustration of a control system 88 anda user input and display console 90 that can be used with ellipticalexercise apparatus 10 or other similar elliptical exercise apparatus toimplement the invention. In this particular embodiment of the controlsystem 88, a microprocessor 92 is housed within the console 90 and isoperatively connected to the alternator 42 via a power control board 94.The alternator 42 is also operatively connected to a ground through loadresistors 96. A pulse width modulated output signal on a line 98 fromthe power control board 94 is controlled by the microprocessor 92 andvaries the current applied to the field of the alternator 42 by apredetermined field control signal on a line 100, in order to provide aresistive force which is transmitted to the pedal 12 and to the arm 80.When the user steps on the pedal 12, the motion of the pedal 12 isdetected as a change in an RPM signal which represents pedal speed on aline 102. It should be noted that other types of speed sensors such asoptical sensors can be used in machines of the type 10 to provide pedalspeed signals. Thereafter, as explained in more detail below, theresistive force of the alternator 42 is varied by the microprocessor 92in accordance with the specific exercise program selected by the user sothat the user can operate the pedal 12 as previously described.

The alternator 42 and the microprocessor 92 also interact to stop themotion of the pedal 12 when, for example, the user wants to terminatehis exercise session on the apparatus 10. A data input center 104, whichis operatively connected to the microprocessor 92 over a line 106,includes a brake key 108, as shown in FIG. 3, that can be employed bythe user to stop the rotation of the pulley 38 and hence the motion ofthe pedal 12. When the user depresses the brake key 108, a stop signalis transmitted to the microprocessor 92 via an output signal on the line106 of the data input center 104. Thereafter, the field control signal100 of the microprocessor 92 is varied to increase the resistive loadapplied to the alternator 42. The output signal 98 of the alternatorprovides a measurement of the speed at which the pedal 12 is moving as afunction of the revolutions per minute (RPM) of the alternator 42. Asecond output signal on the line 102 of the power control board 94transmits the RPM signal to the microprocessor 92. The microprocessor 92continues to apply a resistive load to the alternator 42 via the powercontrol board 94 until the RPM equals a predetermined minimum which, inthe preferred embodiment, is equal to or less than 5 RPM.

In this embodiment, the microprocessor 92 can also vary the resistiveforce of the alternator 42 in response to the user's input to providedifferent exercise levels. A message center 110 includes analpha-numeric display screen 112, shown in FIG. 3, that displaysmessages to prompt the user in selecting one of several pre-programmedexercise levels. In the preferred embodiment, there are twenty-fourpre-programmed exercise levels, with level one being the least difficultand level 24 the most difficult. The data input center 104 includes anumeric key pad 114 and a pair of selection arrows 116, shown in FIG. 3,either of which can be employed by the user to choose one of thepre-programmed exercise levels. For example, the user can select anexercise level by entering the number, corresponding to the exerciselevel, on the numeric keypad 114 and thereafter depressing a start/enterkey 118. Alternatively, the user can select the desired exercise levelby using the selection arrows 116 to change the level displayed on thealpha-numeric display screen 112 and thereafter depressing thestart/enter key 118 when the desired exercise level is displayed. Thedata input center 104 also includes a clear/pause key 120, show in FIG.3, which can be pressed by the user to clear or erase the data inputbefore the start/enter key 118 is pressed. In addition, the exerciseapparatus 10 includes a user-feedback apparatus that informs the user ifthe data entered are appropriate. In this embodiment, the user feed-backapparatus is a speaker 122, that is operatively connected to themicroprocessor 92. The speaker 122 generates two sounds, one of whichsignals an improper selection and the second of which signals a properselection. For example, if the user enters a number between 1 and 24 inresponse to the exercise level prompt displayed on the alpha-numericscreen 112, the speaker 122 generates the correct-input sound. On theother hand, if the user enters an incorrect datum, such as the number100 for an exercise level, the speaker 122 generates the incorrect-inputsound thereby informing the user that the data input was improper. Thealpha-numeric display screen 112 also displays a message that informsthe user that the data input was improper. Once the user selects thedesired appropriate exercise level, the microprocessor 92 transmits afield control signal on the line 100 that sets the resistive loadapplied to the alternator 42 to a level corresponding with thepre-programmed exercise level chosen by the user.

The message center 110 displays various types of information while theuser is exercising on the apparatus 10. As shown in FIG. 3, thealpha-numeric display panel 124, shown on FIG. 3, is divided into foursub-panels 126A-D, each of which is associated with specific types ofinformation. Labels 128A-K and LED indicators 130A-K located above thesub-panels 126A-D indicate the type of information displayed in thesub-panels 126A-D. The first sub-panel 126A displays the time elapsedsince the user began exercising on the exercise apparatus 10 or thecurrent stride length of the apparatus 10. One of the LED indicators130A or 130K is illuminated depending if time or stride length is beingdisplayed. The second sub-panel 126B displays the pace at which the useris exercising. In the preferred embodiment, the pace can be displayed inmiles per hour, minutes per mile or equivalent metric units as well asRPM. One of the LED indicators 130B-130D is illuminated to indicate inwhich of these units the pace is being displayed. The third sub-panel126C displays either the exercise level chosen by the user or, asexplained below, the heart rate of the user. The LED indicator 130Fassociated with the exercise level label 128E is illuminated when thelevel is displayed in the sub-panel 126C and the LED indicator 130Eassociated with the heart rate label 128F is illuminated when thesub-panel 126C displays the user's heart rate. The fourth sub-panel 126Ddisplays four types of information: the calories per hour at which theuser is currently exercising; the total calories that the user hasactually expended during exercise; the distance, in miles or kilometers,that the user has “traveled” while exercising; and the power, in watts,that the user is currently generating. In the default mode of operation,the fourth sub-panel 126D scrolls among the four types of information.As each of the four types of information is displayed, the associatedLED indicators 130G-J are individually illuminated, thereby identifyingthe information currently being displayed by the sub-panel 126D. Adisplay lock key 132, located within the data input center 104, shown inFIG. 2, can be employed by the user to halt the scrolling display sothat the sub-panel 126D continuously displays only one of the fourinformation types. In addition, the user can lock the units of the powerdisplay in watts or in metabolic units (“mets”), or the user can changethe units of the power display, to watts or mets or both, by depressinga watts/mets key 134 located within the data input center 104.

In the preferred embodiment of the invention, the exercise apparatus 10also provides several pre-programmed exercise programs that are storedwithin and implemented by the microprocessor 92. The different exerciseprograms further promote an enjoyable exercise experience and enhanceexercise efficiency. The alpha-numeric display screen 112 of the messagecenter 110, together with a display panel 136, guide the user throughthe various exercise programs. Specifically, the alpha-numeric displayscreen 112 prompts the user to select among the various preprogrammedexercise programs and prompts the user to supply the data needed toimplement the chosen exercise program. The display panel 136 displays agraphical image that represents the current exercise program. Thesimplest exercise program is a manual exercise program. In the manualexercise program the user simply chooses one of the twenty-fourpreviously described exercise levels. In this case, the graphic imagedisplayed by the display panel 136 is essentially flat and the differentexercise levels are distinguished as vertically spaced-apart flatdisplays. A second exercise program, a so-called hill profile program,varies the effort required by the user in a pre-determined fashion whichis designed to simulate movement along a series of hills. Inimplementing this program, the microprocessor 92 increases and decreasesthe resistive force of the alternator 42 thereby varying the amount ofeffort required by the user. The display panel 136 displays a series ofvertical bars of varying heights that correspond to climbing up or downa series of hills. A portion 138 of the display panel 136 displays asingle vertical bar whose height represents the user's current positionon the displayed series of hills. A third exercise program, known as arandom hill profile program, also varies the effort required by the userin a fashion which is designed to simulate movement along a series ofhills. However, unlike the regular hill profile program, the random hillprofile program provides a randomized sequence of hills so that thesequence varies from one exercise session to another. A detaileddescription of the random hill profile program and of the regular hillprofile program can be found in U.S. Pat. No. 5,358,105, the entiredisclosure of which is hereby incorporated by reference.

A fourth exercise program, known as a cross training program, urges theuser to manipulate the pedal 12 in both the forward-stepping mode andthe backward-stepping mode. When this program is selected by the user,the user begins moving the pedal 12 in one direction, for example, inthe forward direction. After a predetermined period of time, thealpha-numeric display panel 136 prompts the user to prepare to reversedirections. Thereafter, the field control signal 100 from themicroprocessor 92 is varied to effectively brake the motion of the pedal12 and the arm 80. After the pedal 12 and the arm 80 stop, thealpha-numeric display screen 112 prompts the user to resume his workout.Thereafter, the user reverses directions and resumes his workout in theopposite direction.

Two exercise programs, a cardio program and a fat burning program, varythe resistive load of the alternator 42 as a function of the user'sheart rate. When the cardio program is chosen, the microprocessor 92varies the resistive load so that the user's heart rate is maintained ata value equivalent to 80% of a quantity equal to 220 minus the user'sage. In the fat burning program, the resistive load is varied so thatthe user's heart rate is maintained at a value equivalent to 65% of aquantity equal to 220 minus the user's heart age. Consequently, wheneither of these programs is chosen, the alpha-numeric display screen 112prompts the user to enter his age as one of the program parameters.Alternatively, the user can enter a desired heart rate. In addition, theexercise apparatus 10 includes a heart rate sensing device that measuresthe user's heart rate as he exercises. The heart rate sensing deviceconsists of heart rate sensors 140 and 140′ that can be mounted eitheron the moving arms 80 or a fixed handrail 142, as shown in FIG. 1. Inthe preferred embodiment, the sensors 140 and 140′ are mounted on themoving arms 80. A set of output signal on a set of lines 144 and 144′corresponding to the user's heart rate is transmitted from the sensors140 and 140′ to a heart rate digital signal processing board 146. Theprocessing board 146 then transmits a heart rate signal over a line 148to the microprocessor 92. A detailed description of the sensors 140 and140′ and the heart rate digital signal processing board 146 can be foundin U.S. Pat. Nos. 5,135,447 and 5,243,993, the entire disclosures ofwhich are hereby incorporated by reference. In addition, the exerciseapparatus 10 includes a telemetry receiver 150, shown in FIG. 2, thatoperates in an analogous fashion and transmits a telemetric heart ratesignal over a line 152 to the microprocessor 92. The telemetry receiver150 works in conjunction with a telemetry transmitter that is worn bythe user. In the preferred embodiment, the telemetry transmitter is atelemetry strap worn by the user around the user's chest, although othertypes of transmitters are possible. Consequently, the exercise apparatus10 can measure the user's heart rate through the telemetry receiver 150if the user is not grasping the arm 80. Once the heart rate signal 148or 152 is transmitted to the microprocessor 92, the resistive load 96 ofthe alternator 42 is varied to maintain the user's heart rate at thecalculated value.

In each of these exercise programs, the user provides data thatdetermine the duration of the exercise program. The user can selectbetween a number of exercise goal types including a time or a caloriesgoal or, in the preferred embodiment of the invention, a distance goal.If the time goal type is chosen, the alpha-numeric display screen 112prompts the user to enter the total time that he wants to exercise or,if the calories goal type is selected, the user enters the total numberof calories that he wants to expend. Alternatively, the user can enterthe total distance either in miles or kilometers. The microprocessor 92then implements the selected exercise program for a period correspondingto the user's goal. If the user wants to stop exercising temporarilyafter the microprocessor 92 begins implementing the selected exerciseprogram, depressing the clear/pause key 120 effectively brakes the pedal12 and the arm 80 without erasing or changing any of the current programparameters. The user can then resume the selected exercise program bydepressing the start/enter key 118. Alternatively, if the user wants tostop exercising altogether before the exercise program has beencompleted, the user simply depresses the brake key 108 to brake thepedal 12 and the arm 80. Thereafter, the user can resume exercising bydepressing the start/enter key 118. In addition, the user can stopexercising by ceasing to move the pedal 12. The user then can resumeexercising by again moving the pedal 12.

The exercise apparatus 10 also includes a pace option. In all but thecardio program and the fat burning program, the default mode is definedsuch that the pace option is on and the microprocessor 92 varies theresistive load of the alternator 42 as a function of the user's pace.When the pace option is on, the magnitude of the RPM signal 102 receivedby the microprocessor 92 determines the percentage of time during whichthe field control signal 100 is enabled and thereby the resistive forceof the alternator 42. In general, the instantaneous velocity asrepresented by the RPM signal 102 is compared to a predetermined valueto determine if the resistive force of the alternator 42 should beincreased or decreased. In the presently preferred embodiment, thepredetermined value is a constant of 30 RPM. Alternatively, thepredetermined value could vary as a function of the exercise levelchosen by the user. Thus, in the presently preferred embodiment, if theRPM signal 102 indicates that the instantaneous velocity of the pulley38 is greater than 30 RPM, the percentage of time that the field controlsignal 100 is enabled is increased according to Equation 1.

$\begin{matrix}{{{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} = {{{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} + \frac{\begin{matrix}( {( { {{{instantaneous}\mspace{14mu}{RPM}} - {30/}} )/2} )^{2}*}  \\ {{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} )\end{matrix}}{256}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$where field duty cycle is a variable that represents the percentage oftime that the field control signal 100 is enabled and where theinstantaneous RPM represents the instantaneous value of the RPM signal98.

On the other hand, in the presently preferred embodiment, if the RPMsignal 102 indicates that the instantaneous velocity of the pulley 38 isless than 30 RPM, the percentage of time that the field control signal100 is enabled is decreased according to Equation 2.

$\begin{matrix}{{{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} = {{{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} + \frac{\begin{matrix}( {( { {{{instantaneous}\mspace{14mu}{RPM}} - {30/}} )/2} )^{2}*}  \\ {{field}\mspace{14mu}{control}\mspace{14mu}{duty}\mspace{14mu}{cycle}} )\end{matrix}}{256}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$where field duty cycle is a variable that represents the percentage oftime that the field control signal 100 is enabled and where theinstantaneous RPM represents the instantaneous value of the RPM signal102.

Moreover, once the user chooses an exercise level, the initialpercentage of time that the field control signal 100 is enabled ispre-programmed as a function of the chosen exercise level as describedin U.S. Pat. No. 6,099,439.

Manual and Automatic Stride Length Adjustment

In these embodiments of the invention, stride length can be variedautomatically as a function of exercise or apparatus parameters.Specifically, the control system 88 and the console 90 of FIG. 2 can beused to control stride length in the elliptical step exercise apparatus10 either manually or as a function of a user or operating parameter. Inthe examples of FIGS. 1 and 2 the attachment assembly 34 generallyrepresented within the dashed lines can be implemented by a number ofmechanisms that provide for stride adjustment such as the stride lengthadjustment mechanisms depicted in FIGS. 4-7, 8A-D, 9A-D and 10A-D. Asshown in FIG. 2, a line 154 connects the microprocessor 92 to theelectronically controlled actuator elements of the adjustmentmechanisms, in the attachment assembly 34. Stride length can then bevaried by the user via a manual stride length key 156, shown in FIG. 3,which is connected to the microprocessor 92 via the data input center104. Alternatively, the user can have stride length automatically variedby using a stride length auto key 158 that is also connected to themicroprocessor 92 via the data input center 104. In one embodiment, themicroprocessor 92 is programmed to respond to the speed signal on line102 to increase the stride length as the speed of the pedal 12increases. Pedal direction, as indicated by the speed signal can also beused to vary stride length. For example, if the microprocessor 92determines that the user is stepping backward on the pedal 12, thestride length can be reduced since an individuals stride is usuallyshorter when stepping backward. Additionally, the microprocessor 92 canbe programmed to vary stride length as function of other parameters suchas resistive force generated by the alternator 42; heart rate measuredby the sensors 140 and 140′; and user data such as weight and heightentered into the console 90.

Adjustable Stride Programs

Adjustable stride mechanisms make it possible to provide enhancedpre-programmed exercise programs of the type described above that arestored within and implemented by the microprocessor 92. As with thepreviously described exercise programs, the alpha-numeric display screen112 of the message center 110, together with a display panel 136, can beused to guide the user through the various exercise programs.Specifically, the alpha-numeric display screen 112 prompts the user toselect among the various preprogrammed exercise programs and prompts theuser to supply the data needed to implement the selected exerciseprogram. The display panel 136 also displays a graphical image thatrepresents the current exercise program. For example, the graphic imagedisplayed by the display panel 136 representing different exerciselevels can include the series of vertical bars of varying heights thatcorrespond to resistance levels that simulate climbing up or down aseries of hills. In this embodiment, the portion 138 of the displaypanel 136 displays a single vertical bar whose height represents theuser's current position on the displayed series of hills. Adjustablestride length programs can be selected by the user utilizing a strideprogram key 160, as shown in FIG. 3, which is connected to themicroprocessor 92 via the data input center 104.

A first program can be used to simulate hiking on a hill or mountain.For example, the program can begin with short strides and a highresistance to simulate climbing a hill then after a predetermined timechange to long strides at low resistance to simulate walking down thehill. The current hill and upcoming hills can be displayed on thedisplay panel 136 where the length of the stride and the resistancechange at each peak and valley. In one implementation, the initial or uphill stride would be 16 inches and the down hill stride would be 24inches, where the program automatically adjusts the initial stridelength to 16 inches at the beginning of the program. Also, the programcan return the stride length to a home position, for instance 20 inches,during a cool down portion of the program.

A second program can be used to change both the stride length and theresistance levels on a random basis. Preferably, the changes in stridelength and resistance levels are independent of each other. Also in oneembodiment, the changes in stride length occur at different timeintervals than the changes in resistance levels. For example, a randomstride length change might occur every even minute and a randomresistance level change might occur at every odd minute of the program.Preferably, the changes in increments will be plus or minus 2 inches ormore. Again, the program can return the stride length to a homeposition, for instance 20 inches, during a cool down portion of theprogram.

A third program can be used to simulate interval training for runners.In one embodiment, by using stride length changes in the longer stridesand having the processor 92 generates motivating message prompts on thedisplay 136, interval training and the gentle slopes and intervals onewould experience when training as a runner outdoors are mimicked. Forexample, the program spans the stride range of 22″-26″ with an initialwarm-up beginning at 22″ then moving to 24″. Here the program thenalternate between the 24″ and 26″ strides thus mimicking intervals atthe longer strides such as those experienced by a runner in training. Inaddition, the display 136 can alert the user to “Go faster” and “Goslower” at certain intervals. As indicated here, it is preferable thatthe prompts be used to encourage faster and slower pedal speeds. Arepresentative example of such a program is provided below:

Warm-Up:

Prompt “Warm Up” message

Minute 00:00=22″ stride (If machine is not at 22″ at program start-up,then it will adjust to the 22″ stride length at program start.)

Minute 03:00=24″ stride

Minute 03:30=prompt “Go faster” message

Intervals:

Minute 04:00=26″ stride

Minute 08:30=prompt “Go slower” message

Minute 09:00=24″ stride

Minute 10:30=prompt “Go faster” message

Minute 11:00=26″ stride

Minute 15:30=prompt “Go slower” message

where the first change is initiated at the 03:00 minute mark, during thewarm-up phase. Other aspects of this particular interval programinclude: stride adjustment increments of 2″; minimum duration of 10minutes; and repeating the interval phase for the selected duration ofthe program.Operation of the Apparatus

The preferred embodiment of the exercise apparatus 10 further includes acommunications board 162 that links the microprocessor 92 to a centralcomputer 164, as shown in FIG. 2. Once the user has entered thepreferred exercise program and associated parameters, the program andparameters can be saved in the central computer 164 via thecommunications board 162. Thus, during subsequent exercise sessions, theuser can retrieve the saved program and parameters and can beginexercising without re-entering data. At the conclusion of an exerciseprogram, the user's heart rate and total calories expended can be savedin the central computer 164 for future reference. Similarly, the centralcomputer 164 can be used to save the total distance traveled along withthe user's average miles per hour and minutes per mile pace during theexercise or these quantities can be tabulated to show the user's paceover the distance or time of the exercise. In addition, thecommunications board 162 can be used to compare distance traveled orpace for the purpose of comparison with other users on other stepapparatus or even other types of exercise machines in real time inorder, for example, to provide for simulated races between users.

In using the apparatus 10, the user begins his exercise session by firststepping on the pedal 12 which, as previously explained, is heavilydamped due to the at-rest resistive force of the alternator 42. Once theuser depresses the start/enter key 128, the alpha-numeric display screen112 of the message center 110 prompts the user to enter the requiredinformation and to select among the various programs. First, the user isprompted to enter the user's weight. The alpha-numeric display screen112, in conjunction with the display panel 136, then lists the exerciseprograms and prompts the user to select a program. Once a program ischosen, the alpha-numeric display screen 112 then prompts the user toprovide program-specific information. For example, if the user haschosen the cardio program, the alpha-numeric display screen 112 promptsthe user to enter the user's age. After the user has entered all theprogram-specific information such as age, weight and height, the user isprompted to specify the goal type (time or calories), to specify thedesired exercise duration in either total time or total calories, and tochoose one of the twenty-four exercise levels. Once the user has enteredall the required parameters, the microprocessor 92 implements theselected exercise program based on the information provided by the user.When the user then operates the pedal 12 in the previously describedmanner, the pedal 12 moves along the elliptical pathway in a manner thatsimulates a natural heel to toe flexure that minimizes or eliminatesstresses due to unnatural foot flexure. If the user employs the movingarm handle 80, the exercise apparatus 10 exercises the user's upper bodyconcurrently with the user's lower body. The exercise apparatus 10 thusprovides a wide variety of exercise programs that can be tailored to thespecific needs and desires of individual users.

Elliptical Stepping Mechanism

In addition to measuring distance traveled on an elliptical exerciseapparatus such as the apparatus 10 in FIG. 1 that has a fixed pedalpath, the principles discussed above can apply to the calculation ofdistance traveled in an elliptical exercise apparatus that has anadjustable stride length. The ability to adjust the stride length in anelliptical step exercise apparatus is desirable for a number of reasons.First, people, especially people with different physical characteristicssuch as height, tend to have different stride lengths when walking orrunning. Secondly, the length of an individuals stride generallyincreases as the individual increases his walking or running speed. Assuggested in U.S. Pat. Nos. 5,743,834 and 6,027,431, there are a numberof mechanisms for changing the geometry of an elliptical step mechanismin order to vary the path the foot follows in this type of apparatus.

Stride Length Adjustment Mechanisms

The ability to adjust the stride length in an elliptical step exerciseapparatus is desirable for a number of reasons. First, people,especially people with different physical characteristics such asheight, tend to have different stride lengths when walking or running.Secondly, the length of an individuals stride generally increases as theindividual increases his walking or running speed. As suggested in U.S.Pat. Nos. 5,743,834 and 6,027,431, there are a number of mechanisms forchanging the geometry of an elliptical step mechanism in order to varythe path the foot follows in this type of apparatus.

FIGS. 4-7, 8A-D, 9A-D and 10A-D depict a pair of stride adjustmentmechanisms 166 and 166′ which can be used to vary the stride length,i.e. maximum foot pedal displacement, without the need to adjust thelength crank 68. Essentially, the stride adjustment mechanisms 166 and166′ replace the stroke link used to move the pedal lever 50 in earliermachines of the type shown in FIG. 1. This approach permits adjustmentof stride length independent of the motion of the machine 10 regardlessas to whether the machine 10 is stationary, the user is pedalingforward, or pedaling in reverse. One of the significant features of thestride adjustment mechanisms 166 and 166′ is a dynamic link, that is, alinkage system that changes its length, or the distance between its twoattachment points, cyclically during the motion of the apparatus 10. Thestride adjustment mechanisms 166 and 166′ are pivotally attached to thepedal lever 50 by a link crank mechanism 168 at one end and pivotallyattached to the crank extension 72 at the other end. The maximum pedallever's 50 excursion, for a particular setting, is called a stroke orstride. The stride adjustment mechanism 166 and the main crank 68 withthe crank extension 72 together drive the maximum displacement/stroke ofthe pedal lever 50. The extreme points in each pedal lever strokecorrespond to extreme points between the Main Crank Axis 40 and a LinkCrank-Pedal Lever Axis 169. By changing the dynamic phase anglerelationship between the link crank 168 and the crank extension 72, itis possible to add to or subtract from the maximum displacement/strokeof the pedal lever 50. Therefore by varying the dynamic phase anglerelationship between the link crank 168 and the crank extension 72, thestroke or stride of the pedal lever 50 varies the length of the majoraxis of the ellipse that the foot pedal 12 travels.

The preferred embodiment of the stride adjustment mechanism 166 shown inFIGS. 4 and 5 takes full advantage of the relative rotation between thecrank extension 72 and a control link assembly 170 of the strideadjustment mechanism 166 as the user moves the pedals 12. In thisembodiment, attachment adjustment mechanism 166 includes the controllink assembly 170 and two secondary crank arms, the link crank assembly168 and the crank extension 72. The control link assembly 170 includes apair of driven timing-pulley shafts 172 and 174, a pair of toothedtiming-pulleys 176 and 178 and a toothed timing-belt 180 engaged withthe timing pulleys 176 and 178. For clarity, the timing belt is notshown in FIG. 4 but is shown in FIG. 5. Also included in the link crankassembly 168 is a link crank actuator 182. One end of thecrank-extension 72 is rigidly attached to the main crank 68. The otherend of the crank-extension 72 is rigidly attached to the rear driventiming-pulley shaft 174 and the pulley 178. Also, the rear driventiming-pulley shaft 174 is rotationally attached to the rearward end ofthe control link assembly 170. The forward end of the control linkassembly 170 is rotationally attached to the forward driventiming-pulley shaft 172 and pulley 176. The two timing-pulleys 176 and178 are connected to each other via the timing-belt 180. The forwarddriven timing-pulley shaft 172 is pivotally attached to the link crank168, but held in a fixed position by the link crank actuator 182 whenthe actuator 182 is stationary; the link crank 168 operates as if itwere rigidly attached to the forward driven timing-pulley shaft 172. Theother end of the link crank 168 is pivotally attached to the pedal lever50 at the pivot axle 169. As an alternative to directly connecting the alink crank mechanism 168 directly to the pedal lever 50, a method ofattachment to reduce the effects of misalignment can be used such as acompliant mounting assembly 183 as shown in FIG. 18. In this case, thecompliant mounting assembly 183 includes a number of resilientcomponents indicated at 185 secured between a pair of support plates 187that absorb and compensate for any misalignment between the main crank68 and the pedal lever 50. In this particular embodiment of theelliptical step apparatus 10 shown in FIGS. 4 and 5, the main crank 68via a revolute joint on a linear slot supports the rearward end of thepedal lever 50. Here, this is in the form of a roller & track interfaceindicated generally at 184. When the apparatus 10 is put in motion,there is relative rotation between the crank extension/rearwardtiming-pulley 178 and the control link 170. This timing-pulley rotationdrives the forward driven timing-pulley 176 via the timing-belt 180.Since the forward driven timing-pulley 176 is rigidly attached to oneend of the link crank 168, the link crank 168 rotates relative to thepedal lever 50. Because the control link 170 is a rigid body, therotation of the link crank 168 moves the pedal lever 50 in a prescribedmotion on its support system 184. In order to facilitate installation,removal and tension adjustment of the belt 180 on the pulleys 176 and178, the control link 170 includes an adjustment device such as aturnbuckle 186 that can be used to selectively shorten or lengthen thedistance between the pulleys 176 and 178.

In this mechanism 166, there exists a relative angle indicated by anarrow 188 shown in FIG. 4 between the link crank 202 and the crankextension 70. This relative angle 188 is referred to as the LC-CE phaseangle. When the link crank actuator 182 is stationary, the LC-CE phaseangle 188 remains constant, even if the machine 10 is in motion. Whenthe actuator 182 is activated, the LC-CE phase angle 188 changesindependent of the motion of the machine 10. Varying the LC-CE phaseangle 188 effects a change in the motion of the pedals 10, in this case,changing the stride length.

In the embodiment, shown in FIG. 5, the link crank actuator 182 includesa gear-motor, preferably an integrated motor and gearbox 190, a wormshaft 192, and a worm gear 194. Because the link crank actuator 190rotates about an axis relative to the pedal lever 50, a conventionalslip-ring type device 196 is preferably used to supply electrical power,from for example the power control board 94 shown in FIG. 2, across thisrotary interface to the DC motor of the gear-motor 190. When power isapplied to the gear-motor 190, the worm shaft 192 and the worm gear 194rotate. The rotating worm shaft 192 rotates the worm gear 194, which isrigidly connected to the driven timing pulley 176. In addition, the wormgear 194 and the forward pulley 176 rotate relative to the link crank168 to effect the LC-CE Phase Angle 188 change between the crankextension 72 and the link crank 168. A reverse phase angle change occurswhen the motor 190 is reversed causing a reverse stride change, that is,a decrease in stride length. In this embodiment, less than half of the360 degrees of the possible phase angle relationship between the linkcrank 168 and the crank extension 72 is used. In some mechanisms usingmore or the full range of possible phase angles may provide differentand desirable ellipse shapes.

Another embodiment of the stride adjustment mechanism 166′, shown inFIGS. 6 and 7 of the invention takes similar advantage of the relativerotation between the crank extension 72 and a control link assembly 170′of the stride adjustment mechanism 166′ as the user moves the pedals 12.In this embodiment, the stride adjustment mechanism 166′ includes thecontrol link assembly 170′, the link crank assembly 168′ and the crankextension 72′. The control link assembly 170′ includes a set of fourtoothed timing pulleys 198, 200, 202, 204, a pair of back-side idlerpulleys, 206 and 208, and a toothed timing-belt 210 engaged with the allsix pulleys. All of the pulleys are rotationally attached to the controllink plate 212. The back-side idler pulleys, 206 and 208, are rigidlyconnected to each other through a slot 214 in the control link plate212, as shown in FIG. 7 which is a backside view of the control linkassembly 170′ of FIG. 6. Being rigidly connected, the back-side idlerpulleys 206 and 208 can move as a pair along the slot 214. Also includedin the control link assembly 170′ is a linear actuator 216. One end ofthe crank-extension 72 is rigidly attached to the main crank 68. Theother end of the crank-extension 72 is rigidly attached to the reartiming-pulley 204. Also, the rear timing-pulley 204 is rotationallyattached to the rearward end of the control link assembly 170′. Theforward end of the control link assembly 170′ is rotationally attachedto the forward timing-pulley 200. The forward timing-pulley 200 ispivotally attached to the link crank 168′, but held in a fixed positionby the linear actuator 216 when the actuator 216 is stationary. In thiscase, the link crank 168′ operates as if it were rigidly attached to theforward timing-pulley 200. The other end of the link crank 168′ ispivotally attached to the pedal lever. When the apparatus 10 is put inmotion, there is relative rotation between the crank extension 72′rearward timing-pulley 204 and the control link 170′. This timing-pulleyrotation drives the forward driven timing-pulley 200 via the timing-belt210. Since the forward driven timing-pulley 200 is rigidly attached toone end of the link crank 168′, the link crank 168′ rotates relative tothe pedal lever 50. Because the control link 170′ is a rigid body, therotation of the link crank 168′ moves the pedal lever 50 in a prescribedmotion on its support system.

The schematics of FIGS. 8A-D, 9A-D and 10A-D illustrate the effect ofthe phase angle change between the crank extension 72 and the link crank168 for a 180 degree, a 60 degree and a 0 degree phase relationshiprespectively. Also, FIGS. 8A, 9A, and 10A display the crank at 180degree position; FIGS. 8B, 9B, and 10B show the crank at 225 degreeposition; FIGS. 8C, 9C, and 10C show the crank at a 0 degree position;and FIGS. 8D, 9D, and 10D show the crank at a 90 degree position. InFIGS. 8A-D the elliptical path 218 represents the path of the pedal 12for the longest stride; in FIGS. 9A-D the elliptical path 218′represents the path of the pedal 12 for an intermediate stride; and inFIGS. 10A-D the elliptical path 218″ represents the path of the pedal 12for the shortest stride.

In certain circumstances, characteristics of stride adjustmentmechanisms of the type 166 and 166′ can result in some undesirableeffects. Therefore, it might be desirable to implement variousmodifications to reduce the effects of these phenomena. For example,when the stride adjustment mechanism 166 is adjusted to the maximumstroke/stride setting, the LC-CE Phase Angle is 180 degrees. At this180-degree LC-CE Phase Angle setting, the components of the strideadjustment mechanism 166 will pass through a collinear or togglecondition. This collinear condition occurs at or near the maximumforward excursion of the pedal lever 50, which is at or near a maximumacceleration magnitude of the pedal lever 50. At slow pedal speeds, thehorizontal acceleration forces are relatively low. As pedal lever speedsincrease, effects of the condition increase in magnitude proportional tothe change in speed. Eventually, this condition can produces soft jerkinstead of a smooth transition from forward motion to rearward motion.To overcome this potential problem several approaches can be takenincluding: limit the maximum LC-CE phase angle 188 to less than 180degrees, for example, restrict stride range to 95% of mechanicalmaximum; change the prescribed path shape 218 of the foot pedal 12; orreduce the mass of the moving components in the stride adjustmentmechanism 166 and the pedal levers 50 to reduce the acceleration forces.

Another problem can occur when the stride adjustment mechanism 166 is inmotion and where the tension side of the timing-belt 180 alternatesbetween the top portion and the lower portion. This can be described asthe tension in the belt 180 changing cyclically during the motion of themechanism 166. At slow speeds, the effect of the cyclic belt tensionmagnitude is relatively low. At higher speeds, this condition canproduce a soft bump perception in the motion of the machine 10 as thebelt 180 quickly tenses and quickly relaxes cyclically. Approaches todealing with this belt tension problem can include: increase thetiming-belt tension using for example the turnbuckle 186 until the bumpperception is dampened; increase the stiffness of the belt 180; increasethe bending stiffness of the control link assembly 170; and install anactive tensioner device for the belt 180.

A further problem can occur when the stride adjustment mechanism 166 isin motion where a vertical force acts on the pedal lever 50. Themagnitude of this force changes cyclically during the motion of themechanism 10. At long strides and relatively high pedal speeds, thisforce can be sufficient to cause the pedal lever 50 to momentarily liftoff its rearward support roller 70. This potential problem can beaddressed in a number of ways including: install a restrained rearwardsupport such as a linear bearing and shaft system, linear guides railsystem 220, as shown in FIG. 11, roller-trammel system 184, as shown inFIG. 4; limit the maximum LC-CE phase angle 188 to less than 180degrees; restrict stride range to 95% of mechanical maximum; and reducethe mass of the moving components in the stride adjustment mechanism andthe pedal levers.

A third embodiment to modify stride length, as illustrated in FIG. 12,is a pedal actuation assembly 222. In this case, an extension arm 224extends directly from a crank 68′. Because the extension arm 224 extendsto and beyond the pivot axle 40, it is possible to move a pivotalconnection point 226 of the stroke link 228 along the extension arm 224,by a mechanism or actuator depicted at 230 in a slot 232, and along thecrank 68′ to the pivot axle 40. When the connection point 226 is alignedwith the pivot axle 40 the pedal lever 50 will not move in alongitudinal direction thus resulting in a purely vertical movement ofthe foot pedal 12. If the pivot point 226 is moved past the axle 40, thefoot pedal 12 moves in a longitudinal direction opposite of the armhandles 80 shown in FIG. 1. As a result, the pedal actuation assembly222 provides added flexibility to an elliptical step apparatus. Analternate method of providing a stride adjustment capability in thepedal actuation assembly 222 is to fit an actuator 233 to the strokelink 228. The actuator 233 can adjust the length of the stroke link 228,thus changing the distance between a fixed point on the pedal lever 50and the crank 68′ which would change the stride length of the ellipticalpath 218.

FIG. 13 illustrates another elliptical step apparatus 10′ having amodified pedal actuation assembly 222′. Included in the pedal actuationassembly 222′ is a first link 234 pivotally connected to the pedal lever50 at a pivot point 235 and to a crank 68′ at a pivot point 236. Asecond link 238 is pivotally connected at one end to the frame 14′ at apivot 240 and at its other end to the first link 234 at a pivot point242. A detailed description of the operation of this type of actuationassembly 222′ is provided in U.S. Pat. No. 5,895,339. Stride adjustmentis provided by a mechanism such as an actuator 244 fitted on the firstlink 234. By adjusting the mechanism 244 to increase the length of thefirst link 234, the length of the horizontal movement of the pedals 12can be increased.

In addition to manually operable mechanisms such as a pin and holearrangement, there are a number of electorally operated actuators can beused for the actuators 230, 233 and 244. FIGS. 14-16 provide additionalexamples of such actuators.

FIG. 14 is a schematic view of a first actuator 246 that can be mountedfor example on the extension arm 224 or the crank 68′ of the pedalactuation assembly 222 of FIG. 12. In this actuator 246, a hydraulicfluid indicated at 248 contained in a cylinder 250 flows through a line252 to control the position of a piston 254 in the piston cylinder 256which in turn is connected to the extension arm 224 or the crank 68′ bya piston rod 256. Flow of the fluid 248 is regulated by a valve 258. Inthe preferred embodiment of this actuator 246, the valve is opened whenthe extension arm 224 or the crank 68′ is under tension and closed whenthey are under compression. This will serve to lengthen the extensionarm 224 or the crank 68′ thereby increasing stride length. Reducing thelength of the extension arm 224 or the crank 68′ is accomplished byreversing the process. It should be noted that variations on thisactuator 246 can be used such as replacing the hydraulic fluid 248 witha pheonetic magnetic fluid where the fluid is controlled by a flowchannel in the piston 254. One advantage of this actuator 246 is that itdoes not require a source of outside energy to move the piston 254 butonly enough energy to operate the valve 258. This type of actuator canbe especially useful in self powered apparatus where power is onlyobtained from the alternator 42 when a user is moving the pedals 12.

FIG. 15 is a schematic view of a second actuator 260 mounted for exampleon the extension arm 224 or the crank 68′ of the pedal actuationassembly 222. In this embodiment, a spring 262 is attached to extensionarm 224 and to the end the crank 68′. To increase stride length, aswitch or latch (not shown) is opened and the point of attachment of theextension arm 224 on the crank 68′ moves outwardly due to centrifugalforce as the pulley 38 rotates. To decrease stride length, the switch isopened when pulley 38 is not rotating or rotating very slowly and thespring will retract the extension arm 224 towards the pivot axle 40. Aswith the actuator 246, this actuator 260 can be used on a self poweredmachine.

FIG. 16 is a schematic view of a third actuator 264 that can be used forexample on the pedal actuation assembly 222. In this embodiment a pairof extension links 266 are pivotally connected to the extension arm 224and the crank 68′. A magnetic fluid control disk 268 controls theseparation of the extension links 266 and therefore the connection point232 of the extension arm 224 on the crank 68′. As with the actuators246, centrifugal force will move the extension arm 224 outwardly alongthe crank 68′ when the pulley 38 rotates on the axle 40 and the fluiddisk 268 will then hold the extension links 266 and hence the extensionarm 224 in place. Stride length can then be shortened when the pulley 38is stopped and the fluid disk 268 permits a spring 270 to move theextension links 266 toward each other. As with the actuators 246 and260, this actuator 264 can be used on a self powered machine.

Adjustable Stride Length Control

With reference to the control system 88 shown in FIG. 2, a mechanism isdescribed whereby stride length can be controlled by the user orautomatically modified in an elliptical step apparatus where stridelength can be adjusted such as the type of machine 10 shown in FIG. 1.In one aspect of the invention stride length is adjusted to take intoaccount the characteristics of the user or the exercise being performed.In the preferred embodiment of the invention, the control system 88 andthe console 90 of FIG. 3 can be used to control stride length in theelliptical step exercise apparatus 10 either manually or as a functionof a user or operating parameter. In FIG. 1 an attachment assemblygenerally represented within a dashed line 34 can be implemented by anumber of mechanisms that provide for stride adjustment such as thestride adjustment mechanism 166 described above. It should also be notedthat this aspect of the invention can be implemented using various otherstride adjustment mechanisms such as those shown in FIGS. 12-16. Asdepicted in FIG. 2, a line 154 connects the microprocessor 92 to theattachment assembly 34 which in the case of the stride adjustmentmechanism 166 would be the DC motor 190 as shown in FIG. 5. Stridelength can then be varied by the user via a manual stride length key 156which is connected to the microprocessor 92 via the data input center104. Alternatively, the user can have stride length automatically variedby using a stride length auto key that is also connected to themicroprocessor 92 via the data input center 104. In one embodiment, themicroprocessor is programmed to respond to the speed signal on line 102to increase the stride length as the speed of the pedals 12 increases.Pedal direction, as indicated by the speed signal can also be used tovary stride length. For example, if the microprocessor 92 determinesthat the user is stepping backward on the pedals 12, the stride lengthcan be reduced since an individuals stride is usually shorter whenstepping backward. Additionally, the microprocessor 92 can be programmedto vary stride length a function of other parameters such as resistiveforce generated by the alternator 42; heart rate measured by the sensors140 and 140′; and user data such as weight and height entered into theconsole 90.

Another important aspect of the adjustable stride length control is afeedback mechanism to provide the processor 92 with informationregarding the stride length of the apparatus 10. The measurement ofstride length on an elliptical step apparatus can be important for anumber of reasons including insuring that both pedal mechanisms have thesame stride length. In the context of the apparatus 10 shown in FIG. 1stride length information can be transmitted over the line 154 from theattachment assembly 34 to the processor 92.

There are a number of methods of acquiring stride length information theutility of which can be dependent on the particular mechanicalarrangement of the elliptical step apparatus including the mechanism foradjusting stride length. The preferred method for obtaining thisinformation from an apparatus employing the stride adjustment mechanism166 involves the use of the link crank angle 188 as shown in FIG. 4.Referring to FIGS. 1 and 8A, the angular relation between the crankextension 72 and each of the link cranks 168 is proportional to thestride length. A sensor system such as reed switches and magnets can bemounted to each of the cranks 68 and feedback from each, along with thespeed signal on the line 98 from the alternator 42, can be used by theprocessor 92 to calculate stride length of each pedal 12. The link crank168 and crank extension 72 rotate with the same angular velocity becausethey are mechanically linked, but they can trigger their respective reedswitches and magnets at different times depending on the link crankangle 188. For every revolution of the alternator 42, there are a setnumber of AC taps. The number of AC taps between the link crank 168 andthe crank extension 72 triggering their respective reed switches andmagnets can be made into a theoretical chart deriving link crank angle188 and stride length.

With reference to FIG. 11, a second method involves using a linearencoder 272. This method uses the relative motion between the pedallever 50 and a linear guide assembly 220 that replaces the roller 70shown in FIG. 4. The linear guide 220 supports the pedal lever 50 duringits travel. The distance that the linear guide 220 travels along thepedal lever 50 can be related to the stride length. The encoder 272would reside on the pedal lever 50 and the movable mechanism for theencoder will be connected to the linear guide assembly 220. A sensorsystem can be placed on the pedal lever 50 and used as an indexposition. Then, for example, if 3 index pulses are generated, the crank68 will have traveled one complete revolution. The distance traveled bythe linear guide 220 can then be determined by adding the encoder pulsesseen for every 3 index pulses and looking this up in a table that wouldbe created. In this manner the stride length feedback signal can beprovided to the processor 92.

FIG. 17 A-C provides an illustration of a third method of determiningstride length. This method measures the maximum and minimum anglebetween the rocker arms 32 and 32′ and pedal levers 50 and 50′respectively for various stride lengths. These angles, as shown in FIG.17A-C can then be used to determine the stride length of the pedal 12from this angular information. Commercially available shaft angleencoders can be mounted at the pivot points between the pedal levers 50and 50′ and the rocker arms 32 and 32′.

A fourth method of determining stride length can make use of the speedof the pedal lever 50. This method measures the speed of the pedal 12using the tachometer signal on the line 98 through fastest point oftravel on the elliptical path 218 which changes with stride length. Thepedal speed at the bottom most point of travel on the ellipse willincrease as stride length increases. For example, the speed of the pedal12 can be measured by placing 2 magnets on the pedal 12 twelve inchesapart such that the two magnets will cross a certain point in spaceclose to the bottom most point of pedal travel. A sensor can then beplaced at that point in space (in the middle of the unit) such that eachmagnet will trigger the sensor. The number of AC Tap pulses on line 98for example received between the two sensor activation signals can bemeasured and thus the stride length calculated. A Hall effect sensor canbe used as the sensor.

1. A method for equalizing a first pedal stride length and a secondpedal stride length of an elliptical step machine having variable pedalstride lengths comprising the steps of: measuring the stride length ofeach of said pedals; comparing said measured stride lengths of saidfirst and second pedals; and increasing or decreasing at least one ofsaid pedal stride lengths to make the first and second pedal stridelengths equal; wherein a sensor is associated with each of the pedalsand operatively connected to a microprocessor wherein saidmicroprocessor is used to calculate said pedal stride lengths.
 2. Themethod of claim 1 wherein the elliptical step machine is in motion whilesaid first or said second stride length is adjusted.
 3. The method ofclaim 1 wherein said microprocessor determines the amount said first orsecond pedal stride length changes.